One Day
by CharlieSwagron
Summary: This was originally just a cute, fluffy one-shot of what I thought should happen in 6x10, "The Good, the Bad, and the Baby," but I decided to make it multi-chapter.
1. Chapter 1

**Disclaimer: I don't own Castle or any of the characters.**

**A/N: There really aren't any spoilers in here, just what I know from the summary of episode 10 and what promo pictures have come out. Most of this is just purely what **_**I**_** would like to happen when the two take care of a baby. I typed this up without really meaning to so I hope you like it.**

"How is he?" a voice behind Kate asked. She wheeled around and saw Castle standing inside the doorway to the guest bedroom, arms crossed over his chest.

She turned back to stare down at the infant who was currently sound asleep in his crib. A soft smile dawned upon her face. "He's just fine," she replied quietly so as not to wake him. She rested her forearms on the crib railings and relaxed.

Castle joined her by the crib and placed a hand on the small of Kate's back. It was well past midnight and when he'd woken up to an empty bed, Castle had gone in search of his fiancée, guessing correctly where she'd be.

It hadn't taken long for Kate to become accustomed to taking care of the small child that wasn't even theirs. The baby boy had been carried to a church by a mysterious man, who wasn't his father, and then the man died. He'd been murdered. As part of the investigation, Beckett, and by extension Castle, had been ordered to care for the boy to ensure that no harm came to him until they could find his connection to the murdered man and then his real parents, if any were still alive. They didn't even know the child's name and thus had to create one themselves.

"Let's call him Jameson," Castle had told her enthusiastically.

"No, we're not naming the kid after a character from your books, Castle," she'd said sternly.

"Why not? It's a great name."

"It's a pretentious name," she'd retorted. "And that's just _weird._ The character you based off me has sex with the character you based off you and now you want to name the boy after said male character? I don't think so."

Castle had made a face. "Yeah, I guess you're right. That _is_ kind of strange." He'd thought for a moment before saying, "Okay, what about Alex?"

"Too close to your daughter's name," she'd fired back.

"Frank?"

Kate looked unimpressed. "Does 'Frank' really sound like a baby's name to you?"

"What about Tommy, Matthew, David, Daniel?" He paused then exclaimed, "Oh I know: Spartacus!"

She looked at him like he was crazy. "Castle, how the _hell_ do you go from Daniel to Spartacus. On another note, who the hell would even name their child that?"

"Apparently Spartacus's mother would," he told her smugly.

"Yeah, well, that was about 2000 years ago," she said dryly. "What about Lucas? Or Luke for short," Kate had suggested.

Castle had mulled it over for a minute, tossing it around in his head. Finally he had nodded, and said, "Luke it is, then."

Now here they were, standing beside the crib that Castle had bought at a store and assembled rapidly, watching the little boy sleep on his back.

Kate felt the compulsion to touch him so she did. She reached out a hand and ran a finger softly over the sleeping child's cheek. "He's nothing like I'd expected, Castle," she commented quietly.

"I know," he replied. "Even I expected sleepless nights and horrible tantrums and fits. Never would I've thought he'd be one to sleep like a rock at night." The writer watched as his fiancée ran a hand gently down Luke's back that was rising and falling continuously due to his breathing. He gazed lovingly at her and couldn't help but think that she'd make an amazing mom one day. First, though, they needed to have _that_ talk before any kids actually did pop up.

Nudging her lightly, Castle said, "Come on, Kate. Let's go back to bed."

She shook her head. "I can't, Castle. I just can't bring myself to leave him."

"You know he'll still be here when we wake up in the morning, right?"

"Well duh, but I…." she trailed off.

Castle wrapped an arm around her waist. "That's just your maternal instinct, Beckett. You see a small child and you immediately want to care for and protect him. That's why you're basically refusing to leave his crib tonight even though we both know you need sleep."

She hummed her response and was then silent for several moments. Suddenly, she looked at him and spoke. "Will it be like this? When we have kids?"

Castle looked at her, startled. He definitely hadn't expected _her_ to be the one to say anything about potential future kids.

Misreading his surprise as a bad thing, she tried to backpedal. "That is, if you even want kids. I know you already have a grown daughter so it's okay if—"

"Kate," he interrupted. "I would love to have kids with you one day, don't get me wrong. You just surprised me and that's why I sort of jumped like that."

There was wariness in her eyes. "So, even though you have Alexis, you'd still want to raise another child?"

"Of course." He turned his body to face her, grabbing one of her hands. "I've always wanted more than one kid, but recently the only person I want to mother them is you, Kate."

She smiled sheepishly. "I'd kind of like that too. You're the only man I could ever see myself having children with, Castle. _But_…I'm nowhere near ready for them."

"And that's okay," he told her. "Let's focus on actually getting married first before you start popping out six kids."

"Six?" she asked with disbelief. "I don't think I'm gonna do six. Two, maybe, but no more than three."

"Why not? Don't you want a bunch of little Castle babies running around?"

"Excuse me, but _you're_ not the one who would have to squeeze out those six kids through a tiny hole in your body. And besides, I already have a giant Castle baby running around. Why would I want six more?" Kate didn't even bother trying to keep the teasing out of her voice.

"Ha ha, very funny," Castle responded in his normal volume level, momentarily forgetting the other presence in the room.

Luke stirred and began to make whimpering noises. His tiny eyes fluttered open and his whining got louder.

Kate shot her fiancé an annoyed look that read, "Way to go, dumbass," and then bent over to pick up the boy. She cradled him upright with her right arm coming under his bottom to support him, his face pressed into her chest. Her left hand was free to make soothing circles on the infant's back as she rocked slightly back and forth, cooing to him softly.

Castle looked on with a mixture of awe and wonder. He was so in love with this woman and he couldn't wait to start a family with her. If she was like this with a child she hardly knew, what would she be like with their own baby? _Probably inseparable,_ he thought to himself.

Luke finally calmed down and the writer noticed his eyes close. All of his movements stopped as he fell back to sleep as Kate kept rocking him.

Glancing at the man staring at her with love and adoration in his eyes, she said, "Castle, I'm not gonna be able to put him down."

Picking up on her meaning, he replied, "You know that it's not recommended that infant's sleep in their parents' bed with them, right?"

Kate nodded. "I know, but it can't hurt to just try it for one night."

Castle took a couple steps closer to Kate so that the distance between them was almost none existent. He placed two fingers under her chin and lifted her face to his. The inches separating them disappeared as Castle's mouth found hers. It was chaste and fairly quick, but not rushed. They never rushed a kiss like this. One that conveyed how much they cared for one another and how much love was between them.

He pulled back so he wouldn't crush the boy Kate was still holding, put a hand on her back, and then led her out of the guest room, shutting the door behind him. They walked back to their bedroom slowly in order to not awaken the sleeping child as well as to savor the peace and calm of the moment.

Upon reaching their destination, Kate laid the baby in the middle of the bed, swiftly climbing in next to him on his right. Her partner, in every aspect of her life now, laid down on Luke's left so that the boy was sandwiched in between the two adults. He was laying on his back, undisturbed by the fact that he'd been removed from the comfort of Kate's chest.

The badass detective, who could make grown men weep like little girls in interrogation, and the mystery writer, who could describe the goriest, most gruesome death in detail, were now reduced to mush because of a little baby. Both were laying on their sides, facing each other, smiles fixed permanently on their faces. Kate rested her right hand lightly on Luke's stomach, needing to have contact with him. Castle, in turn, covered her hand with his, gazing into her eyes. The intimacy of it all surprisingly didn't scare Kate. It only served to make her want this even more.

As they drifted off to sleep, Castle and Kate kept thinking the same exact thing.

_ One day,_ he thought.

_ One day,_ she promised.

**So what did you think? Feel free to review and let me know. Thank you!**


	2. Chapter 2

**Disclaimer: I don't own Castle or any of he characters.**

**A/N: A couple people asked me to continue this so I gave in and decided to do so. Ihope you like this one just as much as the previous one. Thank you for reviews, favorites, and follows.**

It was just before lunch time and Kate had been sitting at her desk for around an hour, blankly staring at the murder board. To anyone who passed by, you'd think she was trying to put the puzzle pieces together and solve the murder. In actuality, though, her thoughts had been consumed with the little boy back at Castle's loft where Castle himself was watching over him.

They'd argued that morning over who should watch over Luke. Castle was okay with staying home and caring for him, but Kate had wanted to take him so that Castle could finish writing his long overdue chapter. She also secretly wanted to spend more time with the infant while she could. Ryan, in addition to screening any available video or media piece pertinent to the case, was tasked with finding out who the boy really was and if he had any surviving relatives.

An uneasy feeling stirred in her gut as she thought about the consequences of Ryan being able to actually locate an relatives at all. She'd be legally obligated to hand the boy over to them and she wasn't exactly sure she was comfortable with that. The worst part was that she didn't know _why_ she was so uncomfortable. She and Castle had talked a couple nights ago about potentially having kids in the future, and while she was all for it, she didn't want to have to worry about them just yet. So why did the idea of leaving Luke in the hands of another, make her so uneasy?

The detective sighed and rubbed her temples slowly with her fingers. A headache was growing and she was beginning to get hungry. Briefly, she debated on going home and eating lunch with her boys.

_ Whoa, where did _that_ come from?_ she wondered, alarmed. _I only have one boy and while he may act like a child most of the time, he most certainly is not. Luke is _not_ mine and Castle's. He's not,_ she tried convincing herself. She groaned, placed her elbows on her desk, and put her head in her hands. _Taking care of him was _not_ supposed to be this confusing._

Kate was about to reach for her phone and call Castle when she heard the elevator ding, alerting everyone that it was about to open. Glancing up, she spotted her fiancé getting off the elevator, carrying a diaper bag on one shoulder and a baby car seat carrier in the other hand. A grin lit up her face and she stood to greet him.

"Hey," he said. He placed the carrier, Luke strapped inside it, gently on the floor before removing the diaper bag and placing right next to the wide awake baby.

"Hey," she greeted. "What're you doing here?"

"Well, I had just finished my chapter when this one," he gestured to Luke, "woke up from the nap he was taking. I figured since he was hungry and I was hungry, and that you were probably hungry, we'd stop in and the three of us could go out to eat. Your lunch break officially starts in about ten minutes so we can leave then."

Kate stooped down to unstrap Luke from the carrier and said, "I was actually just about to call you when you decided to show up here, unannounced." She shot him a look.

He shrugged. "Don't look at me like that, it was _his_ idea," he told her, pointing at the baby who was currently frowning up at him as if he knew Castle was blaming him.

The detective scoffed. "Yeah, okay, Castle. I'm sure the kid did exactly that. Look," she added. "He's even giving you a disapproving glare."

"He must take after his mother, then," he replied, quite clearly meaning her.

"He's not my son, Castle." Tugging away the restraints on the seat, Kate carefully picked the infant up and cradled him against her chest.

"Well, it certainly looks like you want him to be," a voice behind them sounded.

They turned around and saw Ryan and Esposito coming towards them. "Motherhood looks good on you, Beckett," Esposito remarked with a smirk.

"Shut up," she ordered him. Unconsciously shifting the child higher so that the boy's head was resting in the crook of her neck. She could feel the tiny puffs of air that was his breathing and she smiled slightly.

"You want to hold him?" she asked Ryan, knowing that he would take this seriously considering his wife was relatively close to her due date. He'd been particularly sensitive during this case and had actually been the first one to hold Luke when they arrived at the scene of the crime.

"Are you sure? I don't want to mess anything up," he said self-consciously.

"You're gonna have to get used to holding a baby at some point, Ryan. You might as well start now." With that she carefully handed him over to the other detective, who handled the boy as if he was made of glass and would break.

"See? You didn't kill him," she said.

"Yet," Castle added. He and Esposito shared a laugh and bumped fists.

Kate, though, whacked him on the chest and instructed, "Be nice."

Just then, Ryan's phone rang in his pocket. It was Jenny. "Crap, here," he handed Luke off to Esposito and answered his phone, walking off to have some privacy to talk to his wife.

"No, don't—" Too late. Espo stood there glaring at his partner and awkwardly holding the child.

His boss laughed and shook her head. "Not like that, you idiot; _you're_ the one that'll end up dropping him. She stepped forward and readjusted the boy in his arms.

Castle guffawed at the Latino's wide-eyed expression of fear. "What's the matter, Esposito? Scared of a baby?"

The other man narrowed his eyes at him and replied, "I've been in combat and war zones. I've stared down hardened criminals and blood-thirsty serial killers. I've seen things that _have_ made you scream like a little girl." He scoffed. "I am _not_ afraid of little kid."

Luke shifted in his arms and the man nearly jumped out of his skin, a panicked look overtaking his features momentarily.

The couple in front of him laughed heartily at him. "That wasn't funny!" he insisted. The child shifted again and began fidgeting more and more. Small whimpers sounded from his mouth.

"Someone take this kid from me before I accidentally drop him," Esposito nearly screamed.

"Okay, okay, give him to me," Kate told him. She held out her hands and her friend practically tossed the boy into them. Pulling him in close, she began to make soothing sounds and whispered softly to the boy. Almost immediately, he calmed down.

"Told you motherhood looks good on you, Beckett," Esposito said. This time, he was smiling sincerely.

"Thanks, Espo, but it'll be some time before you'll actually see me popping out a kid," she said wryly. "We're actually about to head out to lunch. Do you want us to stop and pick you guys up anything?"

The Latino shook his head. "Nah, we already ate not too long ago."

"Okay then, I'll be back in a little while. Castle, grab the car seat and bag," she ordered, already walking off with Luke. "Don't let the place burn to the ground while I'm gone, boys," she called behind her.

"We won't," Ryan and Espo said at the same time.

**/-/-/-/-/-/-/-/-/**

Many hours later, Kate stumbled through the door to the loft, weary and exhausted. It had been a long day filled with nothing; no new leads, no suspects, _nothing._ She was frustrated and tired and all she wanted to do was go to bed.

Somehow, she made it to their bedroom, kicked off her heels, and changed into a loose-fitting shirt and pants. About to climb into bed, she suddenly realized that it was eerily quiet in the apartment. Castle's loft was many things, but _silent_ it was never. Something had to be wrong. Grabbing her gun from the drawer she'd put it in earlier, she quietly made her way through the massive place. Taking her time to ascend the steps, she tried to make as little noise as possible. Coming upon the door to the guest bedroom that had been temporarily been transformed into a room fit for a young infant, she paused. Mentally counting to three, she thrust open the door and raised her gun. What she saw made the breath expel from her lungs and her chest tighten.

Luke was currently asleep in the arms of a dozing Castle. The writer was sitting in the cheap rocking chair he'd bought when they first found out they needed to take care of a baby for the duration of their investigation. His head was drooped to one side and his arms firmly encircled the child who was wrapped in a blanket.

Kate immediately lowered her gun, made sure the safety was still on, then tucked it into the waistband of her pants at the small of her back. Padding into the room, she observed the two boys as they slept, completely unaware they were being watched with loving eyes. The detective smiled and moved to relieve Castle from Luke. As she went to lift him up, she felt resistance. Looking down, she saw that Castle was unconsciously tightening his grip on the infant.

_ Always trying to protect someone, even in his sleep,_ she thought amusedly.

She stopped trying to take Luke and decided to wake Castle up instead. "Castle," she called softly. "Castle, wake up."

He stirred and his eyes opened slowly. "Kate?" he asked in his sleep-laden voice.

"Yeah, it's me. Let me take Luke from you."

"M'kay." He relinquished his hold on the bundle in his arms, letting his fiancée kiss him on the forehead and put him in the crib.

"C'mon, Castle. Let's go to bed," she told him.

"But I'm comfy," he protested.

"Yeah, well, you won't be saying that come morning when you're all stiff." She heard him giggle and she sighed exasperatedly. "Not _that_ kind of stiff, pervert. Now come on, or you get to sleep alone tonight."

"Fine, I'm coming." He eased himself out of the rocking chair and grasped Kate's hand, lacing their fingers together and leading them back to their room.

Once there, he flopped into bed on his back. She, however, wasn't nearly as ungraceful as he was. She climbed in, scooting back until she was nearly up against Castle, her back facing him. It was a clear enough signal and he received it. Rolling over on his side, he wrapped a strong arm around her waist, pulling her close. Her back was pressed intimately to his front.

He had been quiet for so long that Kate thought he'd gone back to sleep already. Apparently he hadn't because he broke the silence. "Kate? If we don't find relatives for Luke can we keep him?"

Her heart started beating faster. " 'Keep him'? He's not a dog, Castle."

"Yeah, but…can we? Then we can have a little girl sometime in the future and name her Leia. You know: Luke and Leia, like Star Wars. Then we can get a dog and name him Chewbacca. He's gotta be furry, though. And big, too, 'cause Chewbacca's really furry and big." With that he drifted off to a deep sleep.

Kate laid awake in bed for a little while after Castle had fallen asleep. She was slightly confused, startled, scared, and—dare she say—hopeful about what he'd told her. Most of it, she attributed to his current level of drowsiness which probably caused him to keep what little of a filter he had turned off. When he got extremely tired, he sometimes acted like he was drunk or high, saying things he would never normally say as well as thinking random, abstract thoughts.

The detective stared at the wall, feeling the sleep begin to kick in. Maybe what Castle had said wasn't too bad an idea. Maybe she'd actually be okay if that happened.

_ Maybe, Castle,_ she thought before her eyes closed finally. That night she dreamt of a little boy and little girl with bright blue eyes running around the loft, chasing a big furry dog.

**Let me know what you thought about it? If you have any suggestions about what you might want to see next, please let me know.**


End file.
